as others have said.
If you paid full price for the phone you could of gotten the unlock code right there and then.
Since you left the store i would go to the online chat and ask for the code. Tell them that you brought the phone and they told you they would send it but they never did.
Hopefully you have the recipe for it.
if im wrong tell me. I'd ratter be correct then live life being mislead.
Phone:Note 3 NF1 rooted and stock Knox 0x0
Other Phone(s): T-mobile G1 < HTC Vision G2 < LG-P999 G2x < T989 S2 < HTC One m7 < Note 3